Previous reporting periods saw development of a small animal scintigraphic imaging device capable of planar and SPECT imaging of single photon emitting radiopharmaceuticals. Work during this period centered on adding the third, and final, capability intended for this system, the imaging of positron emitting tracers. Accordingly, the detector modules for the single photon system were configured into a novel, single slice ultra high resolution PET tomograph capable of imaging small, tracer-containing structures in animals the size of the rat. This system underwent extensive bench top testing and preliminary evaluation in small animals. During the process of bringing this system to fruition, it was recognized that unconventional configurations of the detector modules could enhance system performance in unexpected ways, an observation that may have implications in human PET imaging with scintillation cameras as well as in small animals.